A significant number of complex repair jobs... (CR)

[gtckim]

A significant number of complex repair jobs carried out by Ace Repairs have to be reworked under the company’s warranty. The reworked jobs are invariably satisfactory. When initial repairs are inadequate, therefore, it is not because the mechanics lack competence; rather, there is clearly a level of focused concentration that complex repairs require that is elicited more reliably by rework jobs than by first-time jobs.

The argument above assumes which of the following?

A. There is no systematic difference in membership between the group of mechanics who do first-time jobs and the group of those who do rework jobs.
B. There is no company that successfully competes with Ace Repairs for complex repair jobs.
C. Ace Repairs’ warranty is good on first-time jobs but does not cover rework jobs.
D. Ace Repairs does not in any way penalize mechanics who have worked on complex repair jobs that later had to be reworked.
E. There is no category of repair jobs in which Ace Repairs invariably carries out first-time jobs satisfactorily.

OA is A.

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I'm having trouble understanding why D is incorrect - using the negation technique, I get the following interpretation for D:

"Ace Repairs does penalize mechanics who have worked on complex repair jobs that later had to be reworked"

Isn't this negated form challenging/contradicting the conclusion that the difference between the first job and the rework is due to the focus-requiring nature of the rework? As in, if there is fear of penalty for the rework, the mechanics performing the rework obviously has extra incentive to do a better job.

I originally chose A, but on further analysis decided this was a trap choice due to the wording of the answer. The answer states that there is no "systematic difference in membership..." -- I interpreted "membership" as referencing the difference in the number of mechanics in the respective groups, not difference in quality.

Please point out the flaws in my reasoning above. I'm trying to be more systematic about my approach to CR (especially the F/A questions) but often find that my over-analysis leads me down the wrong path. However since in CR the smallest words can make a difference, I find it extremely difficult not to overanalyze.

EDIT 1

OK I thought about this problem more, and though I still have some issues with the wording in A, I think I got D to a point where it is a worse choice than A.

I thought about D in the light of the definition of assumptions, and asked myself whether the author really needs to assume D to be true to draw his/her conclusion. When thought about in that context, I realized that D has several flaws. For example, D states that there are penalties for bad performance on reworks, but there could just as well been penalties for bad work for the original job (the question stem does not refute this possibility). If that were true, than the operators would have similar or identical incentives to do the work correctly, thus negating the incentive.

I think I answered my own question, but I would appreciate still appreciate some critique on my analysis and the wording issue I mentioned for choice A.

[RonPurewal]

your post has ... a lot of words.

in any case, your misunderstanding of choice D stems from the fact that, basically, choice D says 'black' but you read it as 'white'.
consider:

"Ace Repairs does not penalize mechanics who have worked on complex repair jobs that later had to be reworked"

the bold/underlined part refers to the INITIAL jobs, NOT to the re-worked jobs.

so, when you negate this choice, it says that there are penalties for bad INITIAL jobs—a consideration that doesn't help us resolve the issue.
this new statement (the negation) rules out a third possibility—namely, that quality control is more lax on initial jobs because there is no penalty—but it is of no use in judging the 2 possibilities that are actually in the argument.

[RonPurewal]

I interpreted "membership" as referencing the difference in the number of mechanics in the respective groups, not difference in quality.

if there were no other context then this would be a valid interpretation, as the word membership is often used to mean 'number of members'.

here, though, you should have kicked this interpretation to the curb because of the word 'systematic'. a 'systematic difference' is a difference that occurs consistently throughout a large sample.

if "difference in membership" means 'one number minus another number' then it refers to exactly ONE statistic, and thus we get absolute nonsense by putting 'systematic' in front of it.

[RonPurewal]

I'm trying to be more systematic about my approach to CR

this could be either good or fatally crippling, depending on what you mean by 'approach'.

if you mean that you're trying to organize your thoughts better and/or to think in more precise terms, then it's a GOOD thing.

on the other hand, if you mean that you're trying to use 'rules', 'patterns', and/or 'templates' to actually solve the problems, then... well, no.
there's a name for the effort to replace human thinking with 'rules'.
it's called 'strong artificial intelligence'...
...and it does not exist.

if 'thinking more systematically' means that you're trying to replace your own everyday common sense with 'patterns' or 'rules', then your failure is guaranteed.

[RonPurewal]

OK I thought about this problem more, and though I still have some issues with the wording in A, I think I got D to a point where it is a worse choice than A.

that red thing...
...no.
not how the problems are written.

on GMAT CR, EVERY wrong answer is ... a wrong answer.
i.e.,
• a wrong answer will NEVER be 'good, but just not as good as the correct answer'.
• a wrong answer would NEVER become correct if someone stole the correct answer.
etc.

if you think that one of the wrong answers 'has some correctness', then you are misunderstanding something fundamental about it.
this is definitely the case here. choice D is about the original jobs—and you read it as having to do with exactly the opposite set of jobs. whoops.

i'm going to go ahead and guess that this happened because you were reading too fast.
read slowly. yes, you have the time. (i can almost guarantee that you can read faster than i can.)

• try reading some random articles (from a journal or scientific magazine, say) at various speeds.

• find the fastest reading speed at which you still have FULL comprehension. (that's FULL as in 100 per cent. if you have 99 per cent comprehension then you are reading too fast.)

• then DO NOT EVER read faster than this speed.

[gtckim]

Ron - thanks for your responses. As you mentioned, I had originally (incorrectly) categorized Ace Repairs jobs into two: first jobs and complex repair jobs (i.e., rework). After reading your comments regarding this and re-reading the passage, I realize that complex repairs refer to ALL of the jobs that Ace Repairs performs and the correct distinction is between first jobs and reworks.

Regarding you comment about incorrect CR answers -- is this applicable to even weaken/strengthen questions? It's easy to see that for F/A type and more "direct" question types, there is only one correct answer, not varying degrees as I incorrectly implied. However, I think I phrased my question in such a way because some weaken/strengthen questions direct us to choose the most correct answer.

[RonPurewal]

no. the wrong answers will still be %100.0000000 wrong.
as i mentioned, there will NEVER be an answer choice that 'would become correct if you took away the current OA'.

on a WEAKEN question, all four wrong answers will either strengthen the argument or do nothing.

on a STRENGTHEN question, all four wrong answers will either weaken the argument or do nothing.

[RonPurewal]

However, I think I phrased my question in such a way because some weaken/strengthen questions direct us to choose the most correct answer.

the 'most' language is there to be precise.
specifically, some strengthen/weaken/explain questions will have wrong answer choices that go in the right direction but are negligible.

if you encounter such a choice, it will always be 'negligible' FOR SPECIFIC REASONS THAT APPEAR in the passage.

e.g., in OG 13th / 2015 look at #94 (the problem about bamboo).
choice C says that, in order to use bamboo, you have to incur a certain extra cost beyond the cost of the bamboo itself.
if we didn't know the magnitude of that cost then you might face the problem you're describing here... but compare 'at some expense' (in choice C) vs. 'MUCH less expensive' (in the passage).
thus C does essentially nothing.

i'm including these choices under 'do nothing', because they have NO power to strengthen/weaken/explain anything. (even if choice B were not there on #94, choice C is still negligible. it still can't explain the thing.)

[AnirbanR136]

If we negate option D, it would be something like this
Ace repair penalizes mechanics for complex works that have to be re-worked.
Does this not rule out the possibility of "lacking focused concentration" required for complex works, leaving us with one possibility which is incompetence among mechanics
So does negation of D not weaken the arguement?

[tim]

What if D did weaken the argument? Remember, if you're using the negation test, the negation of the correct answer must render the conclusion impossible, not just weaken it.

[RonPurewal]

if you negate D, that doesn't weaken the argument -- it just makes the FACTS seem really weird and improbable. (if mechanics were penalized for jobs that had to be re-worked, then we would expect pretty much the opposite of the pattern described in the facts.)

the problem, of course, is that FACTS are FACTS and can't be "weakened".
...so, negating D basically does nothing at all to the argument.
it just makes us want to shrug our shoulders and say "hmm, that's really odd" (in reference to the given FACTS)... but, those FACTS are still FACTS.

[jabgt]

I'm trying to be more systematic about my approach to CR

this could be either good or fatally crippling, depending on what you mean by 'approach'.

if you mean that you're trying to organize your thoughts better and/or to think in more precise terms, then it's a GOOD thing.

on the other hand, if you mean that you're trying to use 'rules', 'patterns', and/or 'templates' to actually solve the problems, then... well, no.
there's a name for the effort to replace human thinking with 'rules'.
it's called 'strong artificial intelligence'...
...and it does not exist.

if 'thinking more systematically' means that you're trying to replace your own everyday common sense with 'patterns' or 'rules', then your failure is guaranteed.

Hi Ron,

Thanks a lot for this advice! I had spent one whole month to study "Logic Reasoning Bible" of LSAT, but I didn't improve my rate of correctness nor speed of resolving problem -- I tried to match each suspicious problem to common flaws in the reasoning I have learnt, feeling exhausted after every single problem. I have finally seen the great difference between the required abilities of the two exams with checking explanations and following advice from you.

Really thank you so much!

BR,
Christine

[RonPurewal]

oh, yeah... DEFINITELY don't use LSAT problems. if you study with LSAT problems, you will probably become worse at GMAT critical reasoning.

the two paradigms are COMPLETELY different. the LSAT problems mostly use "formal logic", which is not tested on the GMAT at all.